A class of mental retardation, due to the inherited disorder of sphingolipid metabolism is collectively called sphingolipidoses. We plan to study the nature of the metabolic defects in these disorders. The main objective of this research is to isolate various glycosidases pertinent to the sphingolipidoses and to use the glycosidases to study the catabolism of various sphingoglycolipids such as GM1-ganglioside, GM2-ganglioside and ceramide trihexoside, etc. We have found that the enzyme hydrolysis of sphingoglycolipids by mammalian glycosidases requires a protein-activator to stimulate the reaction. We plan to isolate this activator in large quantity and to study the mechanism of its activation.